1. Field of the Invention
The present invention relates to apparatuses and methods for tactile stimulation. The present invention more particularly relates to a pneumatic device and method for tactile stimulation using pulses of compressible fluid.
2. Discussion of the Prior Art
Tactile stimulation devices operate by inducing activation of the nerve endings and receptors proximate to a subject's skin, commonly either by applying electrical voltage to, or by mechanically stimulating, the surface of the skin. Once a neuron is activated, normal operation involves firing a signal along a neuronal path to the brain where the sensory input signal is ultimately interpreted, for example as a simulated puff or tap.
Tactile stimulation has a number of uses, primarily in the medical field, which include testing and diagnosis as well as therapeutic applications. For example, it is common to correlate tactile stimuli with brain activity to determine whether a neuronal path and/or the brain are functioning properly, such as in stroke victims, and/or to provide therapy using patterns of tactile stimulation. Where brain activity is recorded in response to tactile stimuli, it is typically detected using functional magnetic resonance imaging (fMRI), magnetoencephalography scanning (MEG), or the like. Subjects' physical responses elicited by tactile stimulation devices, such as reflexive movements, may also or alternatively be measured. Additional information on somatosensory stimulation and its applications can be found in U.S. Publication No. 2012/0157895 A1 (Barlow et al.), which is hereby incorporated by reference in its entirety.
It is common to refer to a graph of stimulus levels (whether stimulus levels are measured by amplitude in volts, pressure/force or other units) over time as a “waveform,” with such stimulus levels being susceptible of measurement at a variety of locations but most commonly at an application site. Different pulse waveforms, for example rectangles or parabolas, and frequencies are desirable for different applications and objectives.
Known tactile stimulation devices that rely on electrical current to carry pulses that induce neuronal signal firing typically do so by driving current to an application site where it is either applied to the skin directly via an electrode or the like, or where it is used to actuate a physical intermediary that translates the current into mechanical motion and contact with the subject. An example of the latter type is a coil wrapped around a cylinder, where the current-bearing coil interacts with an existing magnetic field to induce movement of the cylinder toward the skin of a subject. Electrical current tactile stimulation devices suffer from shortcomings which include the possibility of interference with brain activity measurements and discomfort for the subjects, and difficulty attributing brain activity measurements to bodily responses rather than the stimulation device and its pulse(s).
Known tactile stimulation devices that rely on air as a pulse transfer medium typically comprise a compressor motor for supplying pulses of air to a line directed toward an application site of a subject. Such devices are generally configured so that the compressor motor may be turned on and off to create pressurized pulses at a given frequency for delivery along the line to the application site. Stimulation by these devices may either be effected by direct expulsion of the air pulses onto the subject's skin or other sensory surface (such as the throat) or by an air-actuated physical intermediary affixed to the skin, such as a simple retractable cylinder, that directly translates at least some of the force of the air pulses into mechanical contact with the skin.
Tactile stimulation devices relying on air for delivery of pulses to a subject suffer from a number of shortcomings, including sluggish pulse rise time and imprecise waveforms. It is known to attempt to correct for these shortcomings in applications where pulses travel over relatively long tube passages such as ten to twenty feet by locating a chamber holding compressed air to supply the pulses closer to the application site of the subject. However, such designs may involve increased complexity and cost, and the undesirable placement of additional equipment in “clean” rooms in which measurements are being taken. It is therefore desirable to provide an improved pneumatic device and method for tactile stimulation using pulses of compressible fluid.
This background discussion is intended to provide information related to the present invention which is not necessarily prior art.